Partners' Capital (Schedule of Partners' Capital Account, Distributions) (Details) - USD ($) $ / shares in Units, $ in Millions													9 Months Ended
Aug. 13, 2021	Aug. 06, 2021	May 14, 2021	May 07, 2021	Feb. 12, 2021	Feb. 05, 2021	Aug. 14, 2020	Aug. 07, 2020	May 15, 2020	May 08, 2020	Feb. 14, 2020	Feb. 07, 2020	Sep. 30, 2021	Sep. 30, 2020
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Date of Record		Aug. 06, 2021		May 07, 2021		Feb. 05, 2021		Aug. 07, 2020		May 08, 2020		Feb. 07, 2020
Distribution Made to Limited Partner, Distribution Date	Aug. 13, 2021		May 14, 2021		Feb. 12, 2021		Aug. 14, 2020		May 15, 2020		Feb. 14, 2020
Distribution Made to Member or Limited Partner, Distributions Paid, Per Unit	$ 0.625		$ 0.625		$ 0.625		$ 0.625		$ 0.625		$ 0.625
Distribution Made to Limited Partner, Cash Distributions Paid	$ 39.3		$ 39.3		$ 46.4		$ 45.7		$ 45.7		$ 45.3		$ 125.0	$ 136.7

Amount of cash distribution paid to unit-holder of limited partnership (LP).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

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Date of record for distribution of cash or unit to limited partner of limited partnership (LP), in YYYY-MM-DD format.

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Date of distribution for distribution of cash or unit to limited partner of limited partnership (LP), in YYYY-MM-DD format.

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Per unit of ownership amount of cash distributions paid to unit-holder of a limited partnership (LP).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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